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Date: Tue, 29 Jan 2019 10:45:44 +0100 (CET) From: Thomas Gleixner <tglx@...utronix.de> To: Heiko Carstens <heiko.carstens@...ibm.com> cc: Peter Zijlstra <peterz@...radead.org>, Ingo Molnar <mingo@...nel.org>, Martin Schwidefsky <schwidefsky@...ibm.com>, LKML <linux-kernel@...r.kernel.org>, linux-s390@...r.kernel.org, Stefan Liebler <stli@...ux.ibm.com>, Sebastian Sewior <bigeasy@...utronix.de> Subject: Re: WARN_ON_ONCE(!new_owner) within wake_futex_pi() triggered On Tue, 29 Jan 2019, Heiko Carstens wrote: > On Mon, Jan 28, 2019 at 04:53:19PM +0100, Thomas Gleixner wrote: > > Patch below cures that. > > With your patch the kernel warning doesn't occur anymore. So if this > is supposed to be the fix feel free to add: Yes, it's supposed to be the fix. > > However now I see every now and then the following failure from the > same test case: > > tst-robustpi8: ../nptl/pthread_mutex_lock.c:425: __pthread_mutex_lock_full: Assertion `INTERNAL_SYSCALL_ERRNO (e, __err) != ESRCH || !robust' failed. > > /* ESRCH can happen only for non-robust PI mutexes where > the owner of the lock died. */ > assert (INTERNAL_SYSCALL_ERRNO (e, __err) != ESRCH || !robust); > > I just verified that this happened also without your patch, I just > didn't see it since I started my tests with panic_on_warn=1 and the > warning triggered always earlier. > So, this seems to be something different. Moo. I ran the test loop all night (simply because I forgot to stop it) and of course this does not trigger here. Could you try to gather a bit more information with lightweight tracing? Something like the below should give us at least a clue. Stop the tst loop when the assert triggers and then extract the trace. Thanks, tglx 8<-------------- #!/bin/sh # Substitute with your ld comm string if it starts differently C=ld-linux echo 'comm ~ "$C*"' >/sys/kernel/debug/tracing/events/syscalls/sys_enter_futex/filter echo 'comm ~ "$C*"' >/sys/kernel/debug/tracing/events/syscalls/sys_exit_futex/filter echo 'comm ~ "$C*"' >/sys/kernel/debug/tracing/events/sched/sched_process_exit/filter echo 'prev_comm ~ "$C*" || next_comm ~ "$C*"' >/sys/kernel/debug/tracing/events/sched/sched_switch/filter echo 1 > /sys/kernel/debug/tracing/events/syscalls/sys_enter_futex/enable echo 1 > /sys/kernel/debug/tracing/events/syscalls/sys_exit_futex/enable echo 1 > /sys/kernel/debug/tracing/events/sched/sched_process_exit/enable echo 1 > /sys/kernel/debug/tracing/events/sched/sched_switch/enable
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